Is my flat suitable for a Homeboost/Mainsboost?

[Johntheo5]

The pressure(s) at the washing machine is the one that's required, we can then calculate the minimum pressure there (and make allowance for any difference in elevation depending on where the pump is going to be installed) to see if the pump has enough suction head to avoid cavitation with a high flow demand like the tap+shower. So, can you take the (static) pressure just before starting the test, then with both tap and shower running take the pressure and the tap flowrate, we have the shower flowrate (2.6LPM) with both running.

From your other info then the mains pressure at the washing machine might still be ~ 0.1bar (10M) with both shower and tap running and homebooster installed and should give a ~ shower flowrate of 6.5LPM sufficient for a 40C shower from mains at 20C.
Where do you propose to install the pump in relation to where you have the pressure gauge (elevation).

 

[Ch_152]

The pressure(s) at the washing machine is the one that's required, we can then calculate the minimum pressure there (and make allowance for any difference in elevation depending on where the pump is going to be installed) to see if the pump has enough suction head to avoid cavitation with a high flow demand like the tap+shower. So, can you take the (static) pressure just before starting the test, then with both tap and shower running take the pressure and the tap flowrate, we have the shower flowrate (2.6LPM) with both running.

From your other info then the mains pressure at the washing machine might still be ~ 0.1bar (10M) with both shower and tap running and homebooster installed and should give a ~ shower flowrate of 6.5LPM sufficient for a 40C shower from mains at 20C.
Where do you propose to install the pump in relation to where you have the pressure gauge (elevation).

Ah I see, yeah the pressures measured at washing machine are a few posts up, repeated below for clarity.

~0.9 bar with nothing else open
~0.5 bar with kitchen tap open
~0.6/0.7 bar with upstairs shower running
~0.4 bar with shower running and kitchen tap open.

Just measured the kitchen tap flowrate with shower running, that was around 4.4 L/m.

I also retested the shower, it came out slightly lower (2.1 L/m), but worth noting that my measurements are taken with the shower off the hook and down in the shower tray filling the bucket. When on the hook and at normal showering height, it literally dribbled out.


The pump would be around the same elevation as the washing machine (give or take maybe 20cm).

Cheers for your help, appreciated.

 

[Johntheo5]

Yeah, the Salamander homebooster may be OK, it requires 3.0LPM to start which you have I think with shower only requesting water, I havn't actually seen any pump curves so you might ask them if/what the pump head is at 12LPM, it should be 1.5/1.6bar, the Grundfos UPA50/160 gives pump curves to confirm this, also ask them what is the minimum pump inlet pressure required.

 

[Ch_152]

Yeah, the Salamander homebooster may be OK, it requires 3.0LPM to start which you have I think with shower only requesting water, I havn't actually seen any pump curves so you might ask them if/what the pump head is at 12LPM, it should be 1.5/1.6bar, the Grundfos UPA50/160 gives pump curves to confirm this, also ask them what is the minimum pump inlet pressure required.

Hmm, so actually when my shower is set to eco, it can be less than 3 L/m - so could be an issue for the salamander? (High mode is too hot in summer, when the ambient temp of the mains water is a bit warmer).

Also, those tests were done with the shower head down in the tray, the flow rate with it on the rail are lower and could well be below 3. I’ll have to check when I’m back home on Sunday.

 

[Johntheo5]

You will definitely require 3.5/4.0LPM without the pump installed as there will be a pressure drop through the pump when off, you may only get that with the shower head/hose on the shower tray, messy to say the least as you will also have to put the temperature setting to coldest and then re adjust it when the pump starts, maybe the most pragmatic "solution" is to install a T80SR and just install a 1.5bar pressure relief valve (rather than a pressure reducing valve) anywhere convenient where you can pipe off its outlet to drain.

 

[Madrab]

Not to pour cold water on things (excuse the pun) but I think you need to approach the management/freeholder first to see if pumping the mains is even an option. It is not a given that a pump would be allowed, especially on a common shared main that has a poor supply

I'm sure you wont be the first to suggest this in the building and with the current supply performance, that if more in the building pumped their mains supply that it may struggle to cope with it, others in the building would complain that their supply has dropped, TW would be called and anyone with a pump on the main would be asked to remove it.

Seen it happen a few times before, here in Glasgow, in some of the high tenements with really poor supplies.

Food for thought.

 

[Johntheo5]

So, even the 12LPM limit is a nono??, I presume the extra 3/4LPM via a shower with a integral pump is allowable?

 

[Ch_152]

Not to pour cold water on things (excuse the pun) but I think you need to approach the management/freeholder first to see if pumping the mains is even an option. It is not a given that a pump would be allowed, especially on a common shared main that has a poor supply

I'm sure you wont be the first to suggest this in the building and with the current supply performance, that if more in the building pumped their mains supply that it may struggle to cope with it, others in the building would complain that their supply has dropped, TW would be called and anyone with a pump on the main would be asked to remove it.

Seen it happen a few times before, here in Glasgow, in some of the high tenements with really poor supplies.

Food for thought.

Hi Madrab.

Sorry if I hadn’t mentioned, but each flat has its own metered supply outside the building (I.e managed by TW).

Obviously, at some point upstream, they all come from the same pipe, but I would assume this is somewhat analogous to a street of houses having their own metered supplies.

It was always a thought of mine: what if all the flats (or houses on a street) got pumps? TW permit you to draw up to 12 L/m from the mains (not shared), therefore if most of the houses on the street get pumps and there’s a drop in performance for the houses that didn’t, TW wouldn’t be able to tell you to remove?

It might be worth noting that the flow rate at the Thames Water meter was measured at around 20 to 25 L/m - so the water is there, it’s just not being pushed up to my flat.


But yes, I have emailed management to check. And of course they’re on holiday for the next couple of weeks. Unfortunately, they are not very technically minded and I think I likely to just say no out of principle.


Cheers

 

[Ch_152]

You will definitely require 3.5/4.0LPM without the pump installed as there will be a pressure drop through the pump when off, you may only get that with the shower head/hose on the shower tray, messy to say the least as you will also have to put the temperature setting to coldest and then re adjust it when the pump starts, maybe the most pragmatic "solution" is to install a T80SR and just install a 1.5bar pressure relief valve (rather than a pressure reducing valve) anywhere convenient where you can pipe off its outlet to drain.

I did actually measure this this morning before leaving. Got 3.5 L/m with the shower on eco and the head on the shower rail.

So it would be borderline, and not much wiggle room…

 

[Madrab]

So, even the 12LPM limit is a nono

TW permit you to draw up to 12 L/m from the mains

From a Water Regs point of view, it is allowable for anyone to boost their incoming mains up to a max of 12L/min but in certain circumstances the water transporter (TW) may over ride that, due to the supply not being able to cope with it. It's not a given nor an enforceable law that the transporter have to supply a main that allows everyone that needs to, to boost their incoming supply up to 12L/Min, as in certain circumstance it may just not be possible to allow. Where the supply is this poor I'd always want to check first before proceeding to avoid getting anyone's back up.

That then falls to be reviewed under the heading of a district mains upgrade, if the system is that bad but those things take time and funding

Not saying these circumstance it's like that but I'd always want the client to check first, that keeps everyone informed.

I also appreciate that each property has it's own supply pipe but that just allows TW to meter and charge everyone individually rather than the dynamic mains supply through the communication pipe can actually cope with a higher dynamic draw. Several factors could impact on that - distance from the pumping station - size of district main - level of demand on that main - etc.

 

[Johntheo5]

I did actually measure this this morning before leaving. Got 3.5 L/m with the shower on eco and the head on the shower rail.

So it would be borderline, and not much wiggle room…

The power setting has no influence on the flow rate, did you get that 3.5LPM with the temperature control to its coldest?

 

[Ch_152]

The power setting has no influence on the flow rate, did you get that 3.5LPM with the temperature control to its coldest?

Ah yeah, you're right.

Yeah 3.5 L/m when it's on the coldest. That said, the pipework for the supply is a little convoluted around the cupboard upstairs with the CWS in, and I had thought about getting it re-done if I were to install the pump, which might improve ever so slightly.

 

[Johntheo5]

Grundfos state that the minimum pump inlet required is 2M, 0.2bar, so based on a (kitchen tap) flowrate of 5.1LPM which gave this flowrate at a dP of (0.9-0.5), 0.4bar then the max flow that can be achieved anywhere without pump cavitation is 6.75LPM (0.405m3/hr) with a pump inlet of 0.2bar.

 

[Ch_152]

Grundfos state that the minimum pump inlet required is 2M, 0.2bar, so based on a (kitchen tap) flowrate of 5.1LPM which gave this flowrate at a dP of (0.9-0.5), 0.4bar then the max flow that can be achieved anywhere without pump cavitation is 6.75LPM (0.405m3/hr) with a pump inlet of 0.2bar.

Sorry for the slow reply, busy week at work.

Not sure I follow this. Are you suggesting the Grundfos pump would only give me 6.75 L/m? What about the Salamander?

Also I'm not quite sure I follow the physics of it, if you wouldn't mind explaining to my layman brain...

 

[Ch_152]

Not saying these circumstance it's like that but I'd always want the client to check first, that keeps everyone informed.

Management agency have said they're fine with installing the pump on the mains as long as it doesn't cause a noise nuisance to the adjacent flats.

Which it shouldn't do based on its measured noise level, but may see if I can get some neoprene/rubber lined pipework hangers for the bits next do it which are attached directly to the party wall (single skin block) between flats.